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Chromatography Trail and Investigation

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Chromatography Investigation Aim: I am working for a trading standards office, a local market stall is selling some red and blue sweets that are suspected of containing illegal and possibly toxic colourings. I am going to find out using chromatography whether the dyes are illegal/ legal. Chromatography is a technique which is used for separating and identifying mixtures which are coloured for example, pigments. Chromatography is the collective term for a set of laboratory techniques for the separation of mixtures. It involves passing a mixture dissolved in a mobile phase through a stationary phase, which separates the analyte to be measured from other molecules in the mixture based on differential partitioning between the mobile and stationary phases. Subtle differences in compounds partition coefficient results in differential retention on the stationary phase and thus separation. Reference: http://en.wikipedia.org/wiki/Chromatography#History Equipment List: 250ml Beaker Chromatography Paper Pencil Dyes (Red Food Colouring, Blue Food Colouring, Dylon Red, Dylon Blue) Distilled Water Capillary Tube Ruler Hairdryer Method: 1) ...read more.


Travelled By Component Distance travelled by Water Measurement Errors Ruler % uncertainty = Tolerance x 100 Smallest Measurement 0.5 � 5.75 x 100 = 8.69 No measurement equipment is 100% correct; any measurement equipment will have some sort of measurement error. To calculate the measurement error we need to know the tolerance and then divide it by the smallest measurement (the smaller the measurement the smaller the measurement error) then times this by 100, like the example above. Analysis At the end of my investigation I found out that 2 out of 4 of the dyes were illegal. The two dyes which were found illegal were the red and blue food colouring dyes found in the sweets. The red food colouring dye consisted of two different colours (Pink and Orange) compared to the other which was completely red. The blue food colouring dye consisted of a cyan colour unlike the dylon blue which had a much faded and watery shade of blue. ...read more.


Evaluation This experiment was very interesting; however, I myself during this experiment came across a number of problems. This first problem I came across was trying to use the capillary tubes; the dyes kept on getting mixed with one another because people were reusing the same capillary tubes to drop the dyes onto their chromatography paper. To avoid this problem I myself would have preferred if everyone was given four capillary tubes to use for each dye instead. The second problem I faced was trying to use the dylon blue dye because it was such a faded and watery colour it was very difficult to see whether or not the dye had actually been on the paper, it was also very difficult to measure the dylon blue as it was such a faded colour. To have avoided this problem a darker dye should have been provided for the dylon blue. Besides from these two problems I think that the experiment on a whole was very interesting. ?? ?? ?? ?? Page 1 of 3 ...read more.

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